纳米银复合的掺稀土硫系玻璃薄膜制备及其下转换发光研究

Spectral down-conversion (DC) materials can convert one high energy UV/visible photon which can not be effectively utilized by the c-Si solar cells to two or more near-infrared (near-IR) photons around operating wavelength of the c-Si solar cells. The more near-IR photons emit, the more light will be absorbed by c-Si solar cells, and the higher photovoltaic conversion efficiency will be achieved. However, the most studied DC materials can not be used for c-Si solar cells due to their narrow absorption band of rare earth (RE) ions and the low quantum yield from UV/Visible to near-IR. To solve these problems, the nano-Ag/REs codoped chalcogenide glass films which take advantages of low phonon energy of chalcogenide glass, broad absorption band and local field enhancement (LFE) effect of nano-Ag's SPR will be designed and fabricated. This project will emphasize on the following three aspects, 1) design and fabricate the chalcogenide glass films with high concentration of RE3+/Yb3+(RE=Pr, Tb, Tm)ions co-doping; 2) the technique for preparation of the controllable SPR absorption band position and bandwidth; 3) the influence of SPR absorption and LFE effect of nano-Ag on the DC luminescence properties and quantum yield. Theoretically, the nano-Ag enhanced DC luminescence mechanism of the RE3+/Yb3+ ions codoped chalcogenide glass films will be analyzed by the Judd-Ofelt calculation and Monte Carlo simulation. The aim of the project is to master the technique for fabrication of nano-Ag/REs codoped chalcogenide glass films with broad absorption band and high near-IR emission quantum yield, which will provide the theoretical basis and the scientific data for industrialization of DC materials for c-Si solar cells.

光谱下转换材料可将硅太阳能电池无法有效利用的高能紫外/可见光子转换为可以被其利用的近红外光子，增加硅太阳能电池的吸收效率，从而提高光电转换效率。为解决目前掺稀土光谱下转换材料存在的吸收带窄、近红外发光量子产率低等问题，本项目利用硫系玻璃的低声子能量特性和纳米Ag颗粒的等离子共振(SPR)宽吸收带，借助SPR引起的局域场增强效应，开展纳米Ag复合的掺稀土硫系玻璃薄膜设计、制备及下转换发光性能研究。主要内容包括：高浓度稀土离子掺杂硫系玻璃薄膜研制、纳米Ag的SPR峰位和带宽的可控机理研究、以及SPR对稀土离子下转换发光和量子产率的影响。在理论上结合Judd-Ofelt参数计算和Monte Carlo模拟，建立纳米银颗粒增强的稀土下转换发光模型。旨在获得紫外/可见区域有宽吸收、高近红外量子产率的纳米银复合掺稀土硫系玻璃薄膜材料制备技术，为推动今后下转换材料的产业化提供理论依据和科学的数据。

光谱下转换材料，通过量子裁剪过程，可将一个高能量的光子转换为两个低能量的光子，可用于提高太阳能电池的吸收效率，进而提高光电转换效率。本项目利用硫系玻璃的低声子能量特性和纳米Ag颗粒的等离子共振(SPR)宽吸收带，借助SPR引起的局域场增强效应，开展了纳米Ag复合的掺稀土硫系玻璃薄膜设计、制备及下转换发光性能研究。主要研究了Pr/Yb，Tm/Yb离子掺杂玻璃的发光性能及发光机理，在Pr/Yb掺杂的体系中得到其下转换发光的量子效率可达10.8 %，通过改变激发光功率，证实了1个光子可劈裂成两个光子的量子裁剪过程。项目也研究了纳米Ag析出及纳米晶对稀土发光性能的影响。研究发现Ag纳米颗粒的共振吸收带可调节至500-900 nm之间，尺寸为5-10 nm，对Er3+离子的1.55 μm发光和Tm3+/Ho3+离子的2 μm发光均有荧光增强作用。本项目的研究为今后下转换材料的产业化提供了一定的理论依据和科学的数据。